Glycerin (IUPAC glycerol, also glycerine) is the trivial name and the customary name for propane-1,2,3-triol. Glycerin can be manufactured petrochemically from propylene through the intermediate products allyl chloride and epichlorohydrin, or occurs chemically as a by-product when saponifying natural fats and oils in the synthesis of soaps. Since that time large quantities of glycerin are produced as a by-product of biodiesel manufacturing. This occurs by transesterifying mainly vegetal oils with methanol. A fat molecule (triacyl glyceride) is reacted with three molecules of methanol to afford glycerin and three fatty acid methyl esters (FAME).
Depending on the transesterification process, 100 kg of glycerin are formed per ton of biodiesel. Up to now too few commercial exploitation paths have been available for this glycerin. The traditional areas of application for glycerin in the cosmetic, food, beverage and pharmaceutical industries are largely exhausted.
Consequently, excess amounts of glycerin from biodiesel production are partially disposed of in waste water or burnt for power generation.
Alternative uses are for example biogas generation, chemical transformation into fuels and lubricants or use as a feedstuff additive.
Due to its good chemical reactivity glycerin is also a suitable raw material for the production of chemicals that would otherwise be obtained from petroleum. New glycerin-based production processes, for example for epichlorohydrin or propylene glycol, are under test and processes are under development in numerous research projects in order to open up new fields of application for glycerin as a raw material.
However, few fully developed recovery technologies exist for crude glycerin.
U.S. Pat. No. 7,829,740 B2 describes a process for the production of lactate from glycerin by subjecting the glycerin to a hydrothermal reaction under alkaline conditions.